1). Field of the Invention
This invention relates generally to burn-in board testing and/or other testing boards of electronic devices, and more specifically, to an indirect fuse of such boards.
2). Discussion of Related Art
When fabrication of electronic devices, such as computer processors and memories, has been completed, the electronic devices are subjected to “burn-in” and electrical tests in order to identify and eliminate defective devices before shipment to customers. During testing, a number of these electronic devices, having identical electronic contact layouts, are placed on burn-in boards, and several burn-in boards are placed in a burn-in oven. Electrical signals are transmitted to and from the sockets to test the electronic devices while being heat-stressed in the oven.
Burn-in boards are designed with safety devices to prevent over-current conditions. These safety devices protect critical components by preventing fires and damage to the electronic devices being tested.
The most common safety devices are fuses, current limiting integrated circuits, and polymeric positive temperature coefficient devices. Fuses are consumable items that require inventory management and have a high maintenance cost. Each time a fuse blows, the entire burn-in board is disabled and must be taken out of service. Downtown interrupts production and affects throughput. Current limiting integrated circuits are expensive, sensitive to voltage fluctuations, and susceptible to system program interference. Polymeric positive temperature coefficient devices, in the quiescent state, exhibit a substantial leakage current and circuit resistance, have a maximum operating current of 10 amperes, and cannot operate in an ambient environment of above 100 degrees C.